Envelopes which have a fluid or fluid-like material therein are used for a variety of purposes, one of which is as a padding device for portions of the human anatomy. Particularly in this type of application, the envelope is formed from two layers of substantially flexible material which may be sealed together in a desired shape. However, in order to provide fluid access to the envelope a portion of the perimeter of the envelope remains unsealed such that the fluid may be introduced into the envelope between the two layers. When an appropriate amount of fluid is injected into the envelope, the remainder of the perimeter of the envelope is sealed.
A number of methods which incorporate the above-described types of principles for producing envelopes have been suggested. For instance, "batch"-type processes have been utilized to produce a single envelope. These envelopes are formed either from a single section of material which is appropriately folded to provide two superimposed layers, or from two sections which may be superimposed. Nonetheless, the envelope-forming materials are physically transported, typically by an operator, initially to a first sealing machine to provide a primary definition of the envelope's perimeter and at least one inlet thereto, to a machine for providing fluid to the partially formed envelope, and finally to a second sealing machine to seal off the inlet(s). U.S. Pat. No. 2,470,990 to Kennedy, issued May 24, 1949, discloses one type of "batch" process for simultaneously producing multiple envelopes.
With further regard to Kennedy, generally a heat-sealable sheet of plastic material is folded to provide superimposed layers which are heat sealed together to form a plurality of inflatable articles. These inflatable articles are spaced along both sides of a linear manifold which interconnects such articles and which is also formed by the heat sealing of the superimposed layers. In this configuration, excess material is trimmed and the articles are inflated with a fluid which is introduced at one end of the manifold. When the inlet is thereafter closed, a further heat sealing operation is performed to seal off each of the inflated articles from the manifold such that the inflated articles may be subsequently detached therefrom.
Continuous-type methods are also utilized for producing envelopes generally of the above-described type. More particularly, two continuous sheets of appropriate material are contained on vertically displaced and advancable rolls. The sheets are sealed together, such as by a heat sealing operation, to define a portion of the perimeter of the envelope. An appropriate fluid is then introduced between the sheets by a nozzle which passes between the rolls and thus between the sheets. The sheets are then further sealed to complete the definition of the envelope. In some cases, only a single sealing station is actually utilized such that the second sealing operation for the first envelope being formed actually also provides the initial definition of the second envelope to be formed as well. U.S. Pat. Nos. 3,366,523 to Weber, issued Jan. 30, 1968, 3,575,757 to Smith, issued Apr. 30, 1971, and 4,169,344 to Ganz et al., issued Oct. 2, 1979, are generally representative of dual roll continuous formation processes.